1. Field of the Invention
The present invention relates to a method and device for determining a quality of a clock signal in a slave device.
2. Description of the Related Art
Clock synchronization is a basis for proper operation of process automation and control systems. Typically, each element of an automation system (i.e., a slave device) has an internal clock (driven by a quartz) which has to be synchronized with the clock of an (a priori selected) master device.
Profinet-based systems use a given protocol (based, among others, on the Institute of Electrical and Electronic Engineers (IEEE) standard 1588-2008) to enable synchronization. Here, the synchronization is based on sequentially transmitting SYNC-messages from one element to the next in a chain structure. Locally at the slave device, a control algorithm is used to generate a smooth version of the master time estimate, which is called “controlled time”, and is the output of the local slave device. The controlled time can then be used by other applications as a precise synchronized time for control and/or communication purposes.
However, conventional solutions are neither able to determine the quality of the value of the controlled time nor to detect sudden external disturbances applied to the synchronization hardware, such as vibrations or shocks.